Note 1 - Seneca - School of Information & Communications

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Transcript Note 1 - Seneca - School of Information & Communications

Background History
Note 1
Refer to Soltis: Appendix
Many many years ago
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Over 20 years ago when the S/38 was being developed, the world had never
heard of Microsoft or Netscape.
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The IBM Corporation had experienced the loss of hardware sales to “look alike”
vendors Amdahl and others.
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On the large mainframe front, IBM had just canceled a project known as FS
(Future Systems) that was going be a revolutionary replacement for the existing
line of IBM mainframe computers.
The Rochester Group
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Mid-1960s  At Rochester, Minnesota, a realization that a large market existed
for a small, special purpose business computer. IBM did not share this vision
(System/360 was just announced).
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“The group at Rochester didn’t bother to tell the Corporation they were building a
new computer. Instead, they declared they were building a new unit-record
machine”. Frank Soltis, Chief architect of the AS/400.
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The System/3 was born in 1969 Using RPG (a non-procedural language)
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Enhanced to System/32 (1975), System/34 (1977), System/36 (1983)
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System/38 (1978)  a new concept and architecture
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The AS/400 announced in June 1988.
Why the AS/400
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Businesses typically decide on the application software first, then choose a
computer to run it on. The AS/400 has over 25,000 business applications
worldwide
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The AS/400 is designed and built as a total system, fully integrating all the
hardware and software components that a business needs.
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The AS/400 is a unique system that is defined by software not by hardware.
Instructions have to pass through a layer of microcode before they can be
understood by the hardware itself.
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When a different hardware technology is to be deployed, IBM rewrites sections
of the microcode to absorb the changes in hardware characteristics, so that the
interface presented to the customer remains the same.
A fully integrated system. It’s all in there !
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All the software components : the Operating System, a relational database,
software for comprehensive security, communications subsystems, and Internet
capabilities are already there. On an ordinary machine these software modules
are provided by third parties.
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All the components are designed to work together seamlessly. And are fully
tested as a whole system.
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Easier to install, maintain, and use  Lower operational costs for a business
A Layered Architecture
User Applications Layer
OS/400 System Layer
The MI layer ensures that all
components are fully
integrated. You can not
by-pass the MI layer
MI Microcode Layer
Hardware Layer
AS/400 System Concepts and Architecture
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The AS/400 and the S/38 share the same architectural base : “Capability-based”
addressing and Single-level Storage
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Capability is a pointer to an object in the computer system
The MI interface
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Rather than having the instruction set of the computer being designed by the
engineers, the programmers (the real users of the system) were defining an
instruction set for an abstract machine.
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These instructions rather than be optomized for the hardware were being
designed for writing software applications.
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This abstract machine interface would eventually become known as MI (Machine
Interface) or what IBM currently calls TIMI (technology Independent Machine
Interface).
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This abstract Machine Interface (MI) defined some very advanced concepts to
make programming more efficient and less error prone.
The MI interface
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Programmers would write programs for an abstract machine using new concepts
like not loading data into a hardware registers for processing.
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In this new abstract machine programmers would improve the reliability of
programs by prevented programs from modifying storage to manipulate address
registers.
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Using MI programs could manipulate pointers but the abstract machine would
not allow a change that would cause a pointed to be corrupted.
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This abstract machine interface was being designed to protect programmers
from themselves.
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On previous hardware the programmers knew the addressing structure of
pointers and could even alter memory to change the address (which often was
the cause of program reliability problems).
The iSeries Operating System [OS/400]
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The operating system provides the tools that a user will use to run the AS/400
system
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The major functions of the OS/400 program are:
1.
Control Language
Control language is the set of commands used to talk with the computer.
2.
Data Management
Data management allows the user to define and use data files.
3.
Work Management
Work management controls many jobs, no matter if you are doing several at the same time, or
if other people are using the system.
4.
Programmer Services
Programmer services provide support for online program development and testing.
–
System Operator Services
System operator services provide a menu for easy access to frequently used operator functions.
Cont.
6. Communication Support
The OS/400 program supports a wide range of communication
functions that allow your AS/400 system to communicate with
other types of systems as well as other AS/400 systems.
7. Security
Security protects your valuable work.
8. PC Support
The PC Support program provides a means of attaching your
personal computer to your AS/400 system as a programmable workstation
And many more !!!
Work Management
7. Work Management
There are two types of processing:
° Interactive processing, which requires continuous interaction between
the user and the computer.
° Batch processing, which frees the user and the display station to do
other things once the job has been submitted.
Characteristics of batch jobs:
° Don't need a user (other than to submit a job)
° Don't use display stations (other than to request the job)
° Are always started from a job queue
The Applications Layer
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How does the system user or applications developer interface with the OS/400
on a command level  Control Language (CL)
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CL is a set of OS/400 Commands that control system configuration, system
operation, programming, object management, process management, and
security.
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Has a simple structure: Verb-Object form (a dozen verbs):
Each control language command has the same structure, made up of two
parts:
° Command name
° Parameters
Why the iSeries
iSeries addresses business and infrastructure
needs
Addresses today's IT needs
Establishes the building blocks for
e-business on demand
From Traditional to New Economy
• New Economy  dominant platforms used by companies are Solaris,
Linux, and Windows 2000/XP.
• Traditional brick-and-mortar companies  the AS/400 is still a major
platform.
– need something that's capable of handling heavy transactions.
IBM Series computers